Tensioning means for power strapping machine



Feb. 3, 1970 R. oRaAN ETAL 3,493,014`

TENSIONING MEANS FOR PQWER STRAPPING MAGHINE Filed Sept. 5, 1967 3 Sheets-Sheet l Feb. 3, 1970 R. oRBAN ETAL 3,493,014

TENSIO'NING MEANS FOR POWER STRAPPING MACHINE 3 Sheets-Sheet 2 Filed Sept. 5, 1967 Feb. 3, 1970 R. RBAN ET Al. 3,493,014

TENSIONING MEANS FOR POWER STRAPPING MACHINE I Filed Sept. 5, 1967 3 Sheets-Sheet 5 6 ggg' QuxK-ExH FR'T GRIPPER HOLDING JAW sEALER EE'SON CYL cw. Y 42 73 CYL M92 1 7. 195 7:9 L-`| 5rd no o 69 f JQ )L PRES 11a fz sv-l sv-z Il@ sv-s 7 sv-.4

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@af/5% Geaye-/va United States Patent O U.S. Cl. 140-93.4 5 Claims ABSTRACT OF THE DISCLOSURE A power strapping machine of the type having a motordriven tension roller adapted to tension a metal strap around a package, and having means to crimp a seal around overlapping portions of the strap, is provided with separate tensioning means for exerting high tension on the strap beyond the limit of the tension that can be applied by the motor driven tension roller.

The present invention is specifically directed to the strapping of solid packages, such as bricks and lumber, for example, where high tension is needed. The motordriven tensioning rollers that are normally found on strapping equipment are not able to produce the force necessary to obtain the required high tension. In such situations, it would tend to cause camber and curl, and also causes milling or excessive knurling which would weaken the strap.

In accordance with the present invention, the strap 1s tensioned by a conventional motor-driven tensioning roller to the limit of tension attainable with the motor, and then the high tensioning mechanism exerts a direct pull on the strap, and thus avoids the camber, curl and excessive knurl marks of the tensioning mechanisms previously used. The damage to the strap surface heretofore incidental to high tension is eliminated by the tensioning means of the present invention. The strap lies flatter against the package and thereby enhances the appearance of the package. The high tensioning mechanism does not require close tolerances and may be easily regulated to control the tension applied.

An illustrative embodiment of the invention including structure by means of which the above noted and other advantages of the invention are attained is described in the following specification, taken in conjunction with the accompanying drawings which form a part of this specification and in which:

FIGURE 1 is a fragmentary cross-sectional View of a strapping machine embodying the invention;

FIGURE 2. is a cross-sectional view of one holding jaw mechanism and related face gate mechanism;

FIGURE 3 is a cross-sectional View of the sealer jaw mechanism;

FIGURE 4 is a cross-sectional view of a second holding jaw mechanism;

FIGURE 5 is a cross-sectional view of the front gripping jaw mechanism:

FIGURE 6 is a diagrammatic sketch showing the pneumatic system for controlling the fluid flow to the various components of the strapping machine; and

FIGURE 7 is a yblock diagram of the electrical control circuit.

The present invention may be used with various types of strapping machines. A strapping machine in which the tensioning means of the present invention may be incorporated is fully described in the -Ericsson et al. Patent No. 3,198,218, which was granted Aug. 3, 1965, to the assignee of this invention. Reference may be had to said patent for a more detailed description of struc- ICC ture that is common to this application and the aforesai patent, such as the details of the sealer.

yReferring to the drawings, the strapping mechanisr comprises a strap feeding and tensioning mechanism 1( a gripping and lower holding jaw mechanism 20, a; upper holding jaw mechanism 30, a seal feeding mecha nism 40, and a sealing and shearing mechanism 50. Th gripping jaw mechanism engages the strap near it leading end, after it has been wrapped around one pe rimeter of the package, to hold it against movement rela tive to the package when the strap is pulled back t1 tension it. Thejaw holding mechanisms are coplana and hold overlapped portions of the strap in slidin,` engagement in longitudinally spaced areas on opposin sides of the sealing jaw mechanism to provide a straigh line contact relationship between the overlapped portion of the strap through the area of the sealing jaw mecha nism. The seal feeding mechanism 40 positions a sea adjacent the overlapped portions of the strap bet-weer the two jaw holding mechanisms. The sealing and shear ing mechanism 50 crimps the seal around the overlappe( portions of the strap and cuts the supply end portion o; the strap outwardly of the looped portion of the stra; that is held closed by the seal.

The strap feeding and tensioning mechanism 10 cornI prises a lower strap guide 11 and a pair of rollers 11 and 13 rotatably mounted in the guide. The axes of the rollers extend transversely of the guide with the peripheral surfaces of the rollers in engagement. The roller 12 is driven by any suitable reversible motor M, and the roller 13 is a backup roller. The guide comprises a pair of parallel plates 14 secured to opposite longitudinal edges of upper guide memfbers 15 and lower guide member 16. The guide members are spaced apart to provide a passageway for the strap, and have an open end rearwardly of the bight of the rollers 12 and 13. A pair ol short guide members 17 and 18 are mounted between the plates 14 adjacent the bight of the rollers 12 and 13. The guide members 17 and 118 coverage toward the rollers to facilitate feeding the strap from a supply coil to the rollers. The lower strap guide 11 is pivoted, by a pin 19, to a lug 21 depending from a valve housing 22.

The end of the strap guide 11 remote from the rollers 12 and 13 is curved to form a front surface that has a shoulder 23 projecting therefrom. The shoulder 23 engages a shoulder 24, projecting from the inner surface of a front strap guide 25, to hold the strap guide 11 in position. One end of a guide finger 26 is pivotally secured to one end of the guide member 15. The guide finger 26 fills the gap between the lower end of the stem 27 and the front end of the guide 1S when it is down. The guide linger and the inner surface of the front strap guide form part of a strap chute for guiding the leading end of the strap as it passes through the strapping machine.

A face gate 28 and a guiding insert 29 cooperate to guide the leading end of the strap after it has passed the sealing jaw mechanism. A stationary cutting block 31 is positioned in an intermediate portion of the strap chute. A block insert 32, positioned in the strap chute adjacent the cutting block 31, cooperates therewith to guide the strap toward the upper holding jaw mechanism. The inner surface of the face gate 28 is shaped to guide the leading end portion of the strap into juxtaposition with the supply end portion of the strap, and is recessed to receive the outermost portion of the upper jaw holding mechanism 30 so that both portion of the strap can pass through both jaw holding mechanisms.

After the leading end of the strap passes through the upper end of the strap chute, the strap is Wrapped around one perimeter of the package, and its leading end is threaded between the face gate 28 and the front face of front strap guide 25. The strap chute for guiding the ding end of the strap around the package and back J the strapping tool is conventional and is not shown the drawings. The forward movement of the strap riers its leading end through gripping jaws 33 and n into overlapping relationship with the supply end ftion of the strap. The movement of the strap is stopped .omatically at a predetermined point just beyond the per holding jaw mechanism 30. ['he gripping jaws 33 grab the strap adjacent its leadend and hold it against movement while the overlped portions of the strap are held in sliding engageint by the two coplanar jaw holding mechanisms at :as spaced longitudinally of the strap on opposite sides the sealing jaws. The motor driving the roller 12 is 'ersed to remove the slack and apply tension to the ap. The tension is limited by the power of the motor ving the roller 12, and may be substantially equal to i tension usually applied to strapping secured around :kages of various kinds. In connection with very solid zkages, such as brick or lumber, for example, it is deable to apply additional tension to put the strap under gh tension before the overlapping portions of the strap secured together by a metal seal. The motor for driving the roller 12 does not have to be ge because it does not have to pull a high tension. In :ordance with the present invention, a fluid-operated linder and piston assembly 34 applies force to exert a aight pull on the supply end of the strap while the leadg end portion of the strap is held. The direct pull on a supply end of the strap provides the high tension deed. The small size of the motor permits compactness that the strapping tool can t in a small space and can mounted in any position for various types of packages. The assembly 34 grips the supply end portion of the `ap and the leading end portion is held by the gripping vs 33. A large pulling force is then exerted against the pply end portion of the strap. The assembly 34 comises a tension cylinder 35 having an open lower end )sed by a centrally apertured plate 36. The inner surce of the plate 36 is recessed, as indicated at 37, to proie a seat for one end of a compression spring 38. A ston rod 39, extending through a bushing 41 in the lerture of the plate 36, has a piston 42 secured to its d within the cylinder 35. The opposite end of the pisn rod 39 is pivotally secured, by means of a pin 43, an intermediate portion of a high tension gripper 44. pin 45 pivotally secures one end portion of the gripper the plates 14. The piston 42 has an O-ring -46 sealing a peripheral edge to the inner wall surface of the cylder, and has a recess 47 in its inner surface to provide seat for the other end of the spring 38.

The corner of the gripper 44 below the pin 43 is rurled, as indicated at 48, to enable the gripper 44 t0 ld the strap against movement relative thereto when e gripper is in holding position. The guide member Ls an opening 49 large enough to permit the knurled lrface -48 to engage the surface of the portion of the rap exposed through the opening. The operation of the ylinder and piston assembly 34 that moves the knurled xrtion of the gripper 44 into engagement with the top lrface of the strap in the strap guide 11 will be hereinter described.

'Ihe strap guide 11 also includes a spring plunger block l that is secured to the plates 14 by suitable fastening ,embers 52. One end of the block that is located near le pivot 43 has one edge cut away, as indicated at 53, provide clearance for the adjacent end of the gripper 4. The block 51 is apertured near its opposite end to :ceive a spring plunger 54. A compression spring 55 is lased between the spring plunger block 51 and the head 5 ofthe plunger. The head 56 engages the plate 36, and te spring 55 urges the strap guide 11 downwardly. A in 5.7 prejests transversely fhrQueh the plunger 54 on 4 the side of the block 51 opposite the spring 55 to hold the spring at a predetermined degree of compression.

The upper surface of the spring plunger block 51 is substantially Hush with the upper edges of the plates 14, and a switch 58 is secured to the side plate 14 in vertical alignment with an adjustable screw 49 that extends downwardly from the lower surface of the plate 36. `In the lowermost position of the strap guide 11, the adjacent surfaces of the switch 5S and screw 59 are spaced from each other.

The motor M for rotating the roller 12. is secured 'to the strap guide 11. Accordingly, when the motor has applied tension to the strap, by pulling the supp.y rnd portion of the strap as far as possible, its reaction, upon continued operation in the same direction, will move the strap guide 11 pivotally about the pin 19 in a clockwise direction, as viewed in FIGURE l. This pivotal movement of the strap guide 11 will cause the switch 58 to engage the screw 59 and be energized by it. Energization of the switch 58 will shut off the motor and will actuate the cylinder and piston assembly 34 as hereinafter described.

Actuation of the assembly 34 moves the piston 42 downwardly, as viewed in FIGURE l, and causes the piston rod 39 to move the gripper 44 clockwise about the pin until the knurled portion 48 of the gripper is moved into engagement with the surface of the strap exposed through the opening 49. Continued downward movement of the piston rod 39 while the knurled portion of the grigper is in engagement with the strap moves the strap guide 11 counterclockwise about its pivot 19, thereby forcing the strap guide down. Since the leading end portion of the strap is held by the gripping jaws 33, this movement, with the strap conned within the strap guide, tightens the strap around the package and places it under high tension.

The gripping jaw mechanism 33 that holds the leading end portion of the strap as the high tension is applied to it is shown in detail in FIGURE 5. It comprises a piston 61 mounted in a cylinder 78 and secured to one end of a piston rod 62. A ram 63 is connected to the other end of the rod 62. The gripping jaws 33 are connected to the ram 63 by links 64 that are pivotally secured to the ram by a pin 124 and to the jaws 33 by pins 122. The gripping jaws are pivoted intermediate their length, as indicated at 123, so that inward movement of the piston 61 spreads the outer ends of the links 64 to move the jaws 33 into gripping position, and movement of the piston in the opposite direction opens the jaws.

One of the holding jaw mechanisms, shown in FIGURE 4 is associated with the gripping jaw mechanism and comprises holding jaws 65 and 66 that are connected to the ram 63 by links 67 and 68 that are pivoted to the ram by a pin 124. The jaws 65 and 66 are pivoted intermediate their length, as indicated at 125. The pivotal connections of the jaws 65 and 66 cause them to move into their holding positions as the jaws 33 move into strap gripping position.

The other jaw holding mechanism 30, shown in FIG- URE 2, cooperates with the jaw holding mechanism 2t), with which it is complanar, to hold the overlapped portions of the strap in parallel face-to-face relationship through the area in which the sealing and shearing means operates. The jaw holding mechanisms permit the supply end portion of the strap to be retracted while the leading end portion is held securely by the gripping jaws 33.

The jaw holding mechanism 30 comprises a piston 69 mounted in a cylinder 79 and secured to one end of a piston rod 71. A ram 72 is connected to the other end of the piston rod 71 by a pin 82. Two holding jaws 73 and 74 are connected to the ram 72 by means of links 75 and 76, respectively, both of which are pivoted to the fam. 72; 3S nditel at 126. The hpldiug jaws 73 and 7 4 are both pivoted intermediate their length, as indicated at 127, so that both jaws move inwardly to holding position when the piston 69 moves inwardly of its cylinder.

The cylinders 78 and 79 have a common end wall 81 that is apertured to allow both piston rods 62 and 71 to extend therethrough. The other ends of both cylinders are closed by an end wall 83 of a third cylinder 92 hereinafter described in connection with the sealing and shearing mechanism 50.

The seal feeding mechanism 40 comprises a magazine 84 adapted to hold a plurality of metal seals 85 and having an open end adjacent the outer end of the upper jaw holding mechanism 30. A seal pad 86, positioned in the magazine 84 above the seals, is urged toward the discharge end of the magazine by a coiled spring 87 to move the stack of seals in the same direction. The seal pad is pushed in the opposite direction against the action of the spring 87 when the seals are being loaded into the magazine. A seal ejector 88 is pivoted to one end of a pair of arms 89. The other end of each arm 89 is pivoted to the ram 72 of the upper jaw holding mechanism. A pin 90 pivotally connects a spring-pressed plunger 91 to the midsection of the arm 89.

Movement of the ram 72 to the right, as shown in FIGURE l, permits the spring-pressed plunger 91 to move the arm 89 counterclockwise about pin 100. The movement of the arms 89 in this direction moves the ejector 88 across the open discharge end of the magazine. The ejector pushes the seal 85 at the discharge end of the magazine out of the magazine and in the area between the two coplanar jaw holding mechanisms 20 and 30. The ejector moves the seal into alignment with the outer end of the sealing jaws where it is secured around the overlapped portions of the strap by the sealing jaws. The details of the sealing mechanism are not important to an understanding of the present invention and if further information is desired, reference can be made to the aforementioned Ericsson et al. patent.

Movement of the ram 72 in the opposite direction forces the arms 89 in the opposite direction against the action of the spring-pressed plunger 91 and moves the ejector 88 across the discharge end of the magazine in the opposite direction, so that it will not interfere with the sealing operation.

The sealing and shearing mechanism 50 includes the cylinder 92, -which has a plate 93 that is part of the valve housing 22 closing its end opposite the end 83. A piston 94 mounted in the cylinder 92 has one end of a piston rod 95 secured thereto. The piston rod 95 extends through the bottom wall 83 and also through the wall 81 between the cylinders 78 and 79. The plate 93 is apertured, as indicated at 96, and a conduit 97 extends from the aperture 96 to an aperture 77 in the tension cylinder 35 near the end closed by the plate 36. The conduit 97 directs air bled from the cylinder 92, when the piston 94 is moved outwardly, to the cylinder 35 to cushion the piston 42 after the strap is cut.

As shown in FIGURE 3, the end of the piston rod 95 remote from the piston 94 is connected to a ram 98. A pair of sealer jaws 99 and 101 are connected to the ram 98 by links 102 and 103, respectively. Both links 102 and 103 are pivoted to the ram 98 by a pin 128. The jaws 99 and 101 are pivoted intermediate their length, as indicated at 129. A cutting blade 104, slidably secured to the side of the jaw holding mechanism 20 adjacent the sealing and shearing mechanism 50, is moved past the end of the stationary cutting block 31 after the sealing operation. A pin 131 projecting from the mechanism 50 extends through a longitudinally extending slot 132 in the blade 104 and engages one end of the slot 132 to move the blade after the sealing jaws 99 and 101 have crimped the seal 85 around the overlapped portions of the strap. The blade 104 cooperates with the block 31 to shear the supply end portion of the strap outwardly of the loop formed by sealing the overlapped portions of the -stra by the metal seal 85.

In order to separate the strapped package and th strapping tool, it is necessary to move the'face gate late] ally of the strap guide 29 to get it out of the way. Th mechanism for moving the face gate is attached to th jaw holding mechanism 30, and is shown in FIGURE i The face gate 28 is secured to one end of an L-shaped arr 133 that is pivoted at 134. A pin 135 projecting throng the outer end of the arm 133 engages a notch 136 in on end of a plate 137 that is slidably mounted adjacent on side of the ram 72. The surface of the plate 137 cor tiguous to the ram 72 is provided with a longitudinall extending recess 138 that is engaged by one end of th pin 82 that extends beyond the surface of the ram 72.

During the first part of the movement of the pisto: rod 71 when the piston 69 moves to the left in cylinde 79, as shown in FIGURE l, the ram 72, acting througl the links and 76, moves the gripper jaws 73 am 74-l inwardly toward holding position and the recess 131 permits the pin -82 to move without changing the posi tion of the pin 135. When the pin 82 is engaged wit] the opposite end of the recess 138, it moves the plate 13' and the pin 135 in the same direction as the piston rot 71. This swings the arm 133 counterclockwise about tht pivot 134 to move the face gate 28 laterally of the stra] guide 29 to its open position.

In the movement of the piston rod 71 in the oppositr direction, the pin 82 traverses the length of the recesf 138 in the opposite direction before it moves the plate 137 and pin 135. This moves the arm 133 clockwise abou the pivot 134 to swing the face gate 28 into its close( position.

Returning to FIGURE l, it is noted that the ram 9i has a recess 105 in its side adjacent the upper holding jaws, and a latch 106 interengages the recess to prevent operation of the sealer until the ejector and the face gate 28 move out of the way of the sealing mechanism` The latch 106 is pivoted, as indicated at 107, so that it lcan swing out of engagement with the recess 105 wher.

the lower surface of the ram 72 is advanced out of the way of the front edge of the latch.

The pneumatic diagram and the electrical diagram oi the apparatus shown in FIGURES 6` and 7, respectively, will be described in connection with the operation ol the strapping machine. In describing the operation of the strapping machine, it will be assumed that the strapping machine is adjacent one surface of the article or package to be wrapped, and the leading end of the strap has been positioned between the rollers 12 and 13.

The first step in the strapping operation is to close a switch 108 that energizes the motor M to rotate the roller 12 in one direction so as to feed the strap forwardly into the lower strap guide. The leading end of the strap passes through the strap guide 11 and through the strap chute adjacent the front of the strapping machine. Specifically, the leading end of the strap moves upwardly through the space between the front strap guide 25 and the guide finger 26, then between the stationary cutter 31 and the lblock insert 32, and then between the face gate 28 and guiding insert 29. When the leading end of the strap has passed through the space between the face gate 28 and the guiding insert 29, a chute (not shown) 'guides it around one perimeter of the package and between the front surface of the front strap guide 25 and a gate 109 to lead the strap back into the strapping machine. The gate 109 is spaced forwardly of the strap guide 25 and its lower edge is ared outwardly, as indicated at 110, to facilitate reentry of the strap into the strapping machine.

As the leading end of the strap moves through the strapping machine on its second pass, it closes a switch 111. The switch 111 energizes a timer relay 112 that actuates two solenoid valves 113 and 14 after a time delay. The relay 12 is set to stop the feeding movement of strap after a predetermined time interval has passed. a motor and associated `brake is designed so that the tor will feed the correct amount of strap past the sealand gripping jaws. The motor M is then reversed after leading end of the strap passes the gripping jaws 33. e valve114 operates to load the cylinders 78 and 79 one side of the pistons 61 and 69, respectively, and valve 113 serves to bleed the opposite side of the tons.

['he piston 61, operating through the linkage shown in SURE 5, moves the jaws 33 into strap gripping posin and, operating through the linkage shown in FIG- lE 4, moves the jaws 65 and 66 into strap holding sition. At the same time, the piston 69, operating lough the linkage shown in FIGURE 2, moves the vs 73 and 74 into strap holding position. When the motor M is reversed, it exerts a tensioning fce on the supply end portion of the strap through a roller 12 and its backup roller 13. This tensioning 'ce removes the slack from the strap, and then forces u z strap guide 11 clockwise about its pivot 19 against a action of the spring 55. The pivotal movement of z strap guide 11 causes the switch 58 to move into gagement with the screw 59, and pressure of the switch ainst the screw closes the switch.

Closing the switch S8 energizes a control relay '115 at energizes a timer relay 116 and a solenoid valve 117, d deenergizes the motor M. The valve 117 loads the linder 35' on one side of the piston 42 to move the ipper 44 into engagement with the strap confined in e strap guide 11, and to force the strap guide down. 1e gripper 44 holds the strap against slipping during the vement of the lower strap guide and stretches the strap a direct pulling action on the supply end portion therethus putting the strap under high tension that is eater than the maximum tension that can be applied it by the motor M.

When the timer relay 116 is timed out, it energizes solenoid valve 118 to load the cylinder `92 on the piston le of the piston 94, and deenergizes the timer relay 112. 1e latch 106 prevents the piston 94 from actuating the aling mechanism until the holding jaws 73 and 74 are ased and the ejector 88- is moved out of the way of the aling mechanism, so that it will not interfere with the aling operation. The movement of the piston 94 actuates e sealing jaw mechanism to crimp a seal 85 around f'erlapped portions of the strap, and also moves the ltting blade 104 past the cutting edge of the stationary utter 31 to cut the supply end portion of the strap outardly of the seal. Air from the cylinder 92 is bled trough the conduit 97 into the return side of the cylinder 5, so that when the strap is cut, the movement of the ston 42 will be cushioned.

The deenergization of the relay 112 deenergizes all of le valves and also deenergizes the relay 116, to prevent :filling of the strap chute until all the pistons of the arious valves have returned to their initial positions. hen the relay 116 is timed out, the motor will be re- :tivated to ll the strap chute and thus start another ,/cle.

Although We have described a preferred embodiment f the invention in considerable detail, it will be understood that the description thereof is intended to be illustrative, rather than restrictive, as many details of construction may be modified or changed without departing from the spirit or scope of the invention. Accordingly, we do not desire to be restricted to the exact structure described.

What is claimed is:

1. Apparatus for providing a tensioned ligature about an article comprising: means for feeding a length of binding material from a supply of material around the article so that the leading end portion of the length of binding material overlaps the supply end portion thereof; means for gripping said leading end portion to hold it against movement relative to said article; pivotally mounted support structure; rst means mounted on said support structure for retracting said supply end portion for applying an initial tension to said length of binding material, said retracting means being arranged to pivot said support structure in a rst direction when said initial tension has been applied; second means for further retracting said supply end portion for applying a nal tension to said length of binding material in excess of said initial tension; and means responsive to pivotal movement of said support structure in said one direction for pivoting said support structure in an opposite direction and for actuating said second means.

2. Apparatus in accordance with claim 1 in which said second means includes a gripper pivotally mounted on said support structure and positioned to engage said supply end, and wherein said means responsive to pivotal movement of said support structure includes a cylinder and piston assembly connected to said gripper for initially pivoting said gripper into engagement with said supply end and for subsequently pivoting said support structure to apply said final tension.

3. Apparatus in accordance with claim 2 in which said means responsive to movement of said support structure in said one direction includes a switch for energizing said assembly.

4. Apparatus in accordance with claim 2 in which said support structure includes means for guiding said binding material.

5. Apparatus in accordance with claim 2 including means for cushioning the movement of the piston of said cylinder and piston assembly.

References Cited UNITED STATES PATENTS 2,838,992 6/1958 Demler 10U-32 3,023,693 3/1962 Crosby et al. 100-32 3,183,824 5/1965 Cook 1GO- 26 3,198,218 8/1965 Ericsson et al. l40-93-4 3,232,217 2/1966 Harmon et al. 140-93-4 3,272,113 9/1966 Otto 100--32 CHARLES W. LANHAM, Primary Examiner E. M. COMBS, Assistant Examiner U.S. Cl. X.R. -26, 30 

